feat(webui): polish agent output and app discovery

webui/src/hooks/useNanobotStream.ts

@@ -42,6 +42,7 @@ type UIMessageTurnFields = Pick<UIMessage, "turnId" | "turnPhase" | "turnSeq">;
 
 const FILE_EDIT_TOOL_NAMES = new Set(["write_file", "edit_file", "apply_patch"]);
 const STREAM_END_IDLE_DELAY_MS = 1000;
+const BACKGROUND_STREAM_FLUSH_INTERVAL_MS = 1_000;
 
 function turnFieldsFromEvent(
   ev: { turn_id?: string; turn_phase?: UITurnPhase; turn_seq?: number },
@@ -478,9 +479,12 @@ export interface SendAttachment {
 export interface SendOptions {
   cliApps?: OutboundCliAppMention[];
   mcpPresets?: OutboundMcpPresetMention[];
+  quotedContext?: string;
   workspaceScope?: WorkspaceScopePayload | null;
   sideChannel?: boolean;
   finalizeActiveTurn?: boolean;
+  /** Append guidance to the running turn without detaching its active answer segment. */
+  continueActiveTurn?: boolean;
 }
 
 function eventExtendsModelActivity(ev: InboundEvent): boolean {
@@ -548,6 +552,7 @@ export function useNanobotStream(
   const activitySegmentCounterRef = useRef(0);
   const pendingStreamEventsRef = useRef<PendingStreamEvent[]>([]);
   const streamFrameRef = useRef<number | null>(null);
+  const streamTimerRef = useRef<number | null>(null);
   const suppressStreamUntilTurnEndRef = useRef(false);
   const sideChannelTurnIdsRef = useRef<Set<string>>(new Set());
   /** Timer that defers ``isStreaming = false`` after ``stream_end``.
@@ -570,6 +575,10 @@ export function useNanobotStream(
       window.cancelAnimationFrame(streamFrameRef.current);
       streamFrameRef.current = null;
     }
+    if (streamTimerRef.current !== null) {
+      window.clearTimeout(streamTimerRef.current);
+      streamTimerRef.current = null;
+    }
     pendingStreamEventsRef.current = [];
   }, []);
 
@@ -734,6 +743,10 @@ export function useNanobotStream(
       window.cancelAnimationFrame(streamFrameRef.current);
       streamFrameRef.current = null;
     }
+    if (streamTimerRef.current !== null) {
+      window.clearTimeout(streamTimerRef.current);
+      streamTimerRef.current = null;
+    }
     const events = pendingStreamEventsRef.current;
     const finalAnswerText = options?.finalAnswerText;
     const turn = options?.turn ?? {};
@@ -748,37 +761,47 @@ export function useNanobotStream(
         const targetIndex =
           resolveActiveAssistantIndex(next, turn)
           ?? findStreamingAssistantIndex(next, closedAssistantStreamIdsRef.current, turn);
-          if (targetIndex !== null) {
-            const target = next[targetIndex];
-            next = replaceMessageAt(next, targetIndex, {
-              ...target,
+        if (targetIndex !== null) {
+          const target = next[targetIndex];
+          next = replaceMessageAt(next, targetIndex, {
+            ...target,
+            content: finalAnswerText,
+            isStreaming: true,
+            ...turn,
+          });
+        } else {
+          const id = crypto.randomUUID();
+          closedAssistantStreamIdsRef.current.add(id);
+          next = [
+            ...next,
+            {
+              id,
+              role: "assistant",
               content: finalAnswerText,
               isStreaming: true,
               ...turn,
-            });
-          } else {
-            const id = crypto.randomUUID();
-            closedAssistantStreamIdsRef.current.add(id);
-            next = [
-              ...next,
-              {
-                id,
-                role: "assistant",
-                content: finalAnswerText,
-                isStreaming: true,
-                ...turn,
-                createdAt: Date.now(),
-              },
-            ];
-          }
+              createdAt: Date.now(),
+            },
+          ];
         }
+      }
       if (options?.closeAnswerSegment) closeActiveAssistantStream();
       return next;
     });
   }, [applyPendingStreamEvents, closeActiveAssistantStream, resolveActiveAssistantIndex]);
 
   const schedulePendingStreamFlush = useCallback(() => {
-    if (streamFrameRef.current !== null) return;
+    if (streamFrameRef.current !== null || streamTimerRef.current !== null) return;
+    if (document.visibilityState === "hidden") {
+      streamTimerRef.current = window.setTimeout(() => {
+        streamTimerRef.current = null;
+        const events = pendingStreamEventsRef.current;
+        if (events.length === 0) return;
+        pendingStreamEventsRef.current = [];
+        setMessages((prev) => applyPendingStreamEvents(prev, events));
+      }, BACKGROUND_STREAM_FLUSH_INTERVAL_MS);
+      return;
+    }
     streamFrameRef.current = window.requestAnimationFrame(() => {
       streamFrameRef.current = null;
       const events = pendingStreamEventsRef.current;
@@ -788,6 +811,16 @@ export function useNanobotStream(
     });
   }, [applyPendingStreamEvents]);
 
+  useEffect(() => {
+    const flushOnReturn = () => {
+      if (document.visibilityState !== "visible") return;
+      if (pendingStreamEventsRef.current.length === 0) return;
+      flushPendingStreamEvents();
+    };
+    document.addEventListener("visibilitychange", flushOnReturn);
+    return () => document.removeEventListener("visibilitychange", flushOnReturn);
+  }, [flushPendingStreamEvents]);
+
   // Reset local state when switching chats. Do not reset on every
   // ``initialMessages`` update: a brand-new chat can receive an empty/404
   // history response after the optimistic first message has already rendered.
@@ -863,6 +896,12 @@ export function useNanobotStream(
           turn,
         });
         if (suppressStreamUntilTurnEndRef.current) return;
+        if (ev.resuming) {
+          cancelStreamEndTimer();
+          setIsStreaming(true);
+          setMessages((prev) => finalizeStreamedTurn(prev, turn));
+          return;
+        }
         scheduleStreamEndTimer(turn);
         return;
       }
@@ -1144,6 +1183,7 @@ export function useNanobotStream(
 
       const sideChannel = options?.sideChannel === true;
       const finalizeActiveTurn = options?.finalizeActiveTurn === true;
+      const continueActiveTurn = options?.continueActiveTurn === true;
       flushPendingStreamEvents();
       if (finalizeActiveTurn) {
         cancelStreamEndTimer();
@@ -1153,16 +1193,21 @@ export function useNanobotStream(
       if (sideChannel) sideChannelTurnIdsRef.current.add(turnId);
       const previews = hasAttachments ? images!.map((i) => i.preview) : undefined;
       setMessages((prev) => {
-        if (!sideChannel || finalizeActiveTurn) {
+        if ((!sideChannel && !continueActiveTurn) || finalizeActiveTurn) {
           buffer.current = null;
           activeAssistantRef.current = null;
           closedAssistantStreamIdsRef.current.clear();
           clearActivitySegment();
           suppressStreamUntilTurnEndRef.current = false;
+        } else if (continueActiveTurn) {
+          // Guidance belongs to the active backend turn. Preserve the answer
+          // cursor so its resuming stream_end can finalize the text already
+          // shown before the new user row, while starting fresh activity after it.
+          clearActivitySegment();
         }
         const base = finalizeActiveTurn ? finalizeStreamedTurn(prev) : prev;
         return [
-          ...(sideChannel ? base : pruneReasoningOnlyPlaceholders(base)),
+          ...(sideChannel || continueActiveTurn ? base : pruneReasoningOnlyPlaceholders(base)),
           {
             id: crypto.randomUUID(),
             role: "user",
@@ -1182,6 +1227,7 @@ export function useNanobotStream(
       const wireOptions = { ...options, turnId };
       delete wireOptions.sideChannel;
       delete wireOptions.finalizeActiveTurn;
+      delete wireOptions.continueActiveTurn;
       client.sendMessage(chatId, content, wireMedia, wireOptions);
     },
     [cancelStreamEndTimer, chatId, clearActivitySegment, client, flushPendingStreamEvents],